1. Field of the Invention
This invention relates to radiant energy sensors, and more particularly, to an improved radiant energy sensor employing a plurality of elongated detectors, circuitry, and narrow grooves on a crystalline substrate.
2. Description of the Prior Art
In the prior art sensors for radiation in the infrared region such as from 3 to 12 microns in wavelength utilized detectors such as lead tin telluride or mercury cadmium telluride, lead sulfide, lead selenide, or lead telluride which were combined with separate signal processing circuitry which incorporated such features as antiblooming, background subtraction and time delay integration to provide a desired output. The signal processing circuitry could be bipolar, metal oxide silicon (MOS) or charge coupled device (CCD) which are generally fabricated on silicon substrates. The detectors and the signal processing circuitry were assembled incorporating hybrid packaging systems utilizing a handmade interconnection scheme such as wire bonding or epoxied wires. Hybrid packaging systems have a lower sensor packing density, lower reliability and an increased cost as compared to a monolithic integrated circuit containing the entire sensor.
A monolithic structure incorporating both the detectors for infrared radiation and the signal processing circuitry utilizing charge coupled devices was described by J. C. Fraser et al in the Technical Digest of the International Electronic Devices Meeting sponsored by IEEE Group on Electron Devices held in Washington, D.C. (1974). However, poor isolation between extrinsic silicon sensor elements was reported caused by both optical and electrical cross talk between sensor elements resulting in degraded detector sharpness and modulation transfer function (MTF).
An example of a prior art structure which provided minimum optical cross talk and minimum electrical cross talk between sensor elements or detectors is described by F. J. Kaisler et al in U.S. Pat. No. 3,110,816, issued on Nov. 12, 1963 and assigned to the assignee herein. The patent to Kaisler shows a plurality of light pipes, each light pipe condensing the light entering the entrance pupil down to the smaller area of the exit pupil and a plurality of light sensitive detectors positioned to receive light on a one-to-one basis from the exit pupils of corresponding light pipes with each detector being physically and electrically isolated from each other.
It is therefore desirable to provide a completely monolithic infrared sensor including detectors and signal processing circuitry wherein the detectors have high quantum efficiency, minimum optical cross talk and minimum electrical cross talk. Furthermore, it is desirable for a monolithic infrared sensor to have a detector thickness of 1 millimeter or more to provide 60% quantum efficiency and minimum dark current noise. It is desirable to have a plurality of monolithic infrared sensor substrates, each with its detectors located on 50 micron centers or less to provide an array of several thousand detectors to form one forward looking infrared sensor.